The present invention is directed to new contrast agents for ultrasound imaging. Ultrasound imaging (and diagnostic ultrasound, hereinafter referred to collectively as ultrasound imaging) is commonly used to obtain non-invasive information about internal body structures and the function and motion of such structures. When acoustic energy is coupled into an object to be imaged (such as part of a human body), it propagates through the body with a small portion being reflected, scattered, absorbed or otherwise redirected. The properties of this propagation are affected by various acoustic variables, including pressure, density, temperature and particle motion.
A key variable affecting acoustic propagation is impedance, which comprises the product of material density and the propagation speed of acoustic energy in the material. An acoustic reflection occurs when there exists a boundary between materials of differing impedance. Thus, ultrasound imaging allows detection of impedance boundaries, such as those that occur due to the differences in density between bone and muscle or blood and vascular walls.
Considerable effort has been invested in development of ultrasound contrast agents in an effort to improve contrast between various anatomical features, such as between the vascular lumen and surrounding vessel walls. This is particularly important in assessing many myocardial, renal, respiratory, and oncologic diseases, where the ability to visualize small blood vessels enables physicians to accurately identify and assess disease severity. Moreover, when certain agents are injected directly into tissues, such as ablative agents used for destruction of diseased tissue, or instilled into internal body cavities, such as the bladder, it is desirable to be able to observe such agents using ultrasound imaging. Thus, new agents capable of exhibiting ultrasound contrast are needed for these and other medical applications of ultrasound imaging.
Therefore, it is an object of the present invention to meet these characteristics and to overcome the drawbacks in prior methods and agents.